Process of corrosion inhibition with 1-hexyn-3-ol



United States Patent 3 Claims ABSTRACT OF THE DISCLOSURE Effective corrosion inhibition of an aqueous hydrochloric acid solution having a concentration of at least with respect to corrosion of a ferrous metal at a temperature of at least 82 C. with a minimum amount of corrosion inhibitor is effected by having present in the hydrochloric acid solution when it is in contact with the ferrous metal 0.1 to 0.2% by weight of l-hexyn-3-ol which has the structural formula This application is a continuation of application Ser. No. 770,924 now abandoned.

Metal cleaning baths and pickling baths are usually composed of aqueous solutions of inorganic acids such as sulfuric, hydrochloric, and phosphoric acids and are useful in the cleaning of metals and metal alloys, such as aluminum, ferrous metals specifically including steel, Zinc, etc.

In the use of acid baths to remove undesired metal surface coatings, additives or inhibitors in the acid bath are desirable to prevent or inhibit corrosion or erosion of the metal surfaces. If no corrosion inhibitor is present in the acid bath, the results generally will be excessive metal loss, production of undesirable metal surface proporties, and excessive consumption or loss of acid. While it is well-known to use corrosion inhibitors in such acid baths, those inhibitors heretofore used have had certain disadvantages such as, instability at elevated temperatures, toxic and obnoxious properties when used in the acid baths and in certain cases poor metal surface properties resulted from their use. Also, certain prior art inhibitors are difficult to use as they are bulky sticky :solids or viscous liquids; while others have the undesirable proporties of producing excessive foam and they are not soluble or compatible with other compounds used in the corrosive systems. Still other inhibitors result in the metal having poor properties, especially undesirable in electroplating operations, as poor adhesion and discolored surfaces.

It is an object of this invention to provide an improved composition and an improved method for the protection of metal surfaces against erosion or corrosion in aqueous acid solutions.

Another object of this invention is to provide a novel inorganic acid cleaning composition and a method of cleaning metals while substantially preventing or inhibiting acid attack on metal surfaces being cleaned, without interfering with the desired cleaning action.

A further object of the invention is to provide improved metal cleaning baths that may be operated at elevated temperatures.

These and other objects and advantages of this invention will be pointed out or will become apparent from the following description.

In accordance with the present invention the incorporation of a small amount of l-hexyn-S-ol in aqueous in- 3,423,566 Patented Feb. 18, 1969 organic acid solutions has been found to have the desirable property of inhibiting or substantially preventing the corrosive action or attack of the acid upon the metal surface being cleaned. The use of 1-hexyn-3-ol in acid cleaning and pickling baths does not hinder or interfere with the desired action of the acid on the oxide, rust, grease, scale or other undesirable surface material or coating which is to be removed.

The inhibitor of this invention, 1-hexyn-3-ol, is useful, in general, in the inhibition of corrosion of metal sur faces in contact with aqueous acid solutions, for example, in the acidizing of oil wells, electrolytic cleaning baths, electroplating baths, and electrolytic refining of metals as well as in metal cleaning and pickling baths.

The use of 1-hexyn-3-o1 as a corrosion inhibitor for metals in aqueous inorganic acid solutions is advantageous in that 1-hexyn-3-ol is easily soluble in water and can be employed as a corrosion inhibitor over a wide and useful concentration range. When used as an inhibitor 1-hexyn-3-ol does not produce discolored metal surfaces or undesirable properties on the metal surface in contact with the inhibited acid system. Its use as an inhibitor in metal cleaning operations while inhibiting acid attack on the metals will generally results in improved surface properties of the metals. When compared at equal concentrations 1-hexyn-3-ol will generally give better inhibition than other inhibitors. The inhibitor is not toxic or obnoxious when used in aqueous acid solutions; further it does not produce undesirable foam and it is soluble and compatible with other materials usually added to the aqueous acid systems. A further advantage of this inhibitor is that it may be used at elevated temperatures to provide good corrosion inhibition.

The most effective amount of l-hexyn-3-ol to be used in this invention will vary, depending generally upon the particular acid corrosive system, the particular metal exposed to acid, and the amount of acid present in the aqueous solution. The temperature and other characteristics of the acid corrosive system Will also affect the amount of inhibitor to be used.

In general, it has been found that a concentration of l-hexyn-3-ol between 0.025% to 0.5% by weight of the acid corrosive solution is an effective and desirable corrosion inhibiting concentration, with a concentration between 0.05% to 0.2% being of particular advantage.

The inhibitor of this invention, l-hexyn-B-ol, may be advantageously combined with other compounds, such as amine inhibitors; as for example, quaternary ammonium compounds as Arquad T and Arquad 2C manufactured by Armour and Company; rosin-ammonia reaction products, including abietylamine derivatives; coal tar derivatives and heterocyclic nitrogen compounds; primary, secondary and tertiary amines and their alkyl hydroxy derivatives; and the ethylene oxide condensation reaction products of the preceding amines. This combination being useful as a corrosion inhibitor to inhibit or substantially prevent the corrosion of metals in contact with aqueous acid solutions. This amine, 1-hexyn-3-ol' inhibitor combination may be used in concentrations from approximately 0.025% to 0.5% by weight of the aqueous acid solution. The ratio of amine to 1-hexyn-3-ol may vary appreciably, but it has been found that a 1:1 ratio is advantageous. A particular amine Alkyl Pyridine HB available from Union Carbide Chemicals Company and comprising a mixture of lower alkyl pyridines as methyl, ethyl, isopropyl and propyl pyridine is useful in the amine, 1-hexyn-3-ol combination inhibitor. A mixture of Alkyl Pyridine HB and 1-hexyn3-ol comprising 0.1% of each and a total of 0.2% by weight of the aqueous acid corrosive system is effective as a corrosion inhibitor.

The following examples are illustrative of the corrosion inhibiting properties of l-hexyn-3-ol. In the examples the inhibitor concentration is expressed as percent by weight of the aqueous acid solution and the acid concentration is percent by weight of the solution. The method used to determine the inhibiting properties of 1-hexyn-3-ol as set forth in the examples consisted in first cleaning hot rolled mild steel specimen strips (SAE 10104-015, carbon content 0.0 5 %0.20% 2" -x 1" x l i with an average surface area of 0.0313 sq. ft. and an average weight of 15.5 grams. Cleaning was accomplished by rinsing the steel coupons with trichloroethylene, then rubbing the coupon with a cloth wet with trichloroethylene. The steel coupons then were dipped in concentrated hydrochloric acid for one minute followed by an immediate rinse with distilled water. The coupon was dried by rinsing with acetone. The coupons were then 'weighed to obtain the original weight prior to immersion in the corrosive system for a specified time.

Various corrosive systems may be used, for example, (1) hydrochloric acid system 15% HCl maintained at 66 C. (150 F.), (2) sulfuric acid system 15% H S maintained at 86 C. (187 F.), (3) phosphoric acid system 15% H PO maintained at 71 C. (160 B). These systems are generally representative of the aqueous acid corrosive systems usually encountered.

After immersion in the corrosive system for the specified time the coupons were removed, washed with distilled water, rinsed with acetone, air dried and again weighed. In most tests an initial five hour immersion time was used and the coupons after being weighed were again immersed in the corrosive system for a total of twenty-four hours. The cleaning of the immersed coupon was repeated.

Corrosion inhibiting properties may be described conveniently in terms of the corrosion rate. This rate being the metal loss of weight in pounds per square foot per day.

Immersion corrosion rate (lbs./ft. /day) Coupon weight loss, grams 24 hrs/day 454 grams/lb. immersion time, hrs.

surface area, sq. ft.

Example 1 Immersion corrosion rate Inhibitor 5 hours 24 hours 1-hexyn-3-ol O. 049 0. 011 None 1. 642 0.817

Example 2 A group of tests similar to Example 1, wherein the concentration of 1-hexyn-3-ol was varied, were performed. The hydrochloric acid at 66 C. system was used along with steel coupons.

Immersion corrosion rate Inhibitor concentration, percent 5 hours 24 hours Example 3 The following test was conducted at a higher corrosive system temperature. The procedure used was as in the preceding examples, except the mill scale was not partially removed by an acid dip in the preparation of the steel coupons. A solution of 15% hydrochloric acid at a temperature of 82 C. (180 F.) was used. Inhibitor concentration was 0.2%.

Immersion corrosion Inhibitor: rate, 17 hours 1-hexyn-3-ol 0.017 None 1.585

Example 4 The following test utilized the standard procedure outlined previously with steel coupons andv a 15% hydrochloric acid solution maintained at 180 F. (822 C.). Inhibitor concentration was 0.1%

Immersion corrosion rate,

Inhibitor: 24 hours l-hexyn-S-ol 0.012 None (1) The test sample containing no inhibitor exhibited very rapid corrosive action upon the steel with a total weight loss of 11.643 grams or approximately of the original steel coupon; whereas after the same test period of 24 hours the sanlple containing inhibitor still provided substantial protec on.

Example 5 The following test was conducted using the procedure of Example 3, wherein the mill scale was not partially removed by an acid dip in the preparation of the steel "coupons. A solution of 15 hydrochloric acid at a temperature of 82 C. (180 F.) was used. Inhibitor concentration was percent by weight as shown.

Immersion corrosion rate,

As widely different modifications of the invention may be made without departing from the scope and spirit of the invention, it is to be understood that the invention is not to be limited by the foregoing examples and details of description, except as defined by the following claims.

We claim:

1. In aprocess wherein an aqueous hydrochloric acid solution having a concentration of at least 15 is in contact with a ferrous metal at a temperature of at least 82 C., the improvement which effectively inhibits the corrosion of said ferrous metal by said hydrochloric acid solution with a minimum amount of a corrosion inhibitor which comprises having present in said hydrochloric acid solution when it is in contact with said ferrous metal at said temperature 0.1 to 0.2% by weight of 1-hexyn-3-ol.

2. A process as defined in claim 1, wherein said temperature is 82 to C.

3. A process as defined in claim 1, wherein said temperature is about 82 C., and said concentration is 15%.

References Cited UNITED STATES PATENTS 3,049,496 8/ 1962 Monroe et a1. 252-146 3,107,221 10/1963 Harrison et al. 252148 LEON D. ROSDOL, Primary Examiner.

W. SCHULZ, Assistant Examiner.

U.S. C1. X.R. 1343, 41; 252388 

